Induction furnace



Jan, e, 1932. E. F. RUSS INDUCTION FURNACE Fiied March 5, 1928 2Sheets-Sheet l %www Jan. 26, 1932.' I F uss I 1,843,044

INDUCTION FURNACE Filed March 5, 1928 2 Sheets-Sheet 2 Fig. 5

Patented Jan. 26, 1932 PATENT OFFlCE EHIL FBIEDRICH RUSS, OF COLOGNE,GERMANY INDUCTION Application filed Iarch 5, 1928, Serial No.

The invention relates to induction furnaces for melting, annealing andsimilar kinds oi industrial heat treatment. The essential feature of theinvention is, that a part of the secondary circuit is designed as aheating element.

Inthe accompanying drawings:

Figure 1 is a vertical transverse sectional View of an induction urnaceconstructed and arranged in accordance with this invention. Figure 2 isa similar View of a modified form of the same.

Figure 3 is a vertical sectional view on a plane at right angles to thatof Figure 2.

Figure 4 is a vertical sectional view of another modified form of theinvention.

Figure 5 is a similar view showing another modified Construction of theinventon.

Fi ure 6 is a similar view of another modified orm of the invention.

' Figure 7 is a sectional view of the same on a plane at' right anglesto that of Figure 6.

According to the form of the invention shown in Figs. 1-3, the primarywinding 2 is fitted at the bottom of the muflle masonry 1 'upon an ironyoke. The winding is surrounded by a secondary body 3, open at the topin the shape of a horse-Shoe, which is not intended for heating, and istherefore made of large proportions. To the ends of the horse-Shoe 3 isconnected the heating element 4, by which the secondary circuit isclosed.

This heating element 4 consists, according to Fig. 1, of a resistancesheet bent to suitable shape, which lines the muflle walls. Thus, inthis case the four interior surfaces of the muflle are connected inseries in the secondary circuit. The heating element may consist eitherof smooth sheets or, in order to len hen the current path, of sheetsalternative y ribbed or corrugated.

A special increase in the length of the current path is obtained by thepractical application according to Figs. 2 and 3. The heat- 7 ingelement 5 consists of a sheet bent in one len h in the manner of a loopto form a don le wall, forming three interor surfaces of the muflle. Inorder that both sides ofthe double wall may mpart their heat unimpededto the interior of the muflle, they are FUBNAE 259372, and in GermanyApril 20, 1925.

broken by openings 6 displaced the one against the other, as shown inFig. 3.

In the examples described, almost the entire heat of the secondarycircuit is developed in the part designed as a heating element 4:, or 5respectively. The stout secondary element 3, on the other hand, onlyproduces a small quantity of heat, owing to its large section. Thishowever is not lost either, but is rendered useful as floor heating forthe muflie.

According to the form of the invention shown in Fig. 4: the stoutsecondary element 7 is so designed as to heat not only the floor, butalso the sides of the muflie. For this purpose, both sides of themufile, and connected to the heating element 8 only just below the nullecover. In the Construction illustrated, this element is made ofcorrugated iron, in order to lengthen the current path.

The small liberation of heat of the stoutwalled secondary body may, aswell be made use of in a special heat treatment room outside the muffleproper. Thus, according to Fig. 5, for example, there is a preheatingchamber 9 below the muflle, within which the stout secondary body 10 isfreely suspend-- ed. The heating of the mufile may hercby he carried outaccording to Fig. l or any ol" the other forms of the inventondescribed.

If the stout-walled secondary body is not intended to assist in heating,it may be provided with cooling ribs, cooling pins, or the like., Withthe muflie urnace construeted according to Figs. 6 and 7, for instance,llugreater part of the secondary body 11 is situated outside themasonry, and is 'provided with ribs 12 to increase the cooling surface.The heating element 13 closes the seconda'y circit in the manner alreadydescribed al the interier surface of the muflie.

The stout-walled secondary body may be sub-divided completely in theform of rings, disks, helices, or the like, thereby securing in additionto a large cooling surface, a reduction of eddy current losses.

I claim: r

- 1. In a furnace having a muffle, an electrie heating system comprisinga primary winding, a secondary winding, and a rcsistanc'e it is carriedupwards in the masonry, on a sheet forming the wall of the mufliechamber, each face of the resistance sheet being in the form of a doublewall.

2. A furnace as claimed in claim 1, in

5 which each face of the resistance sheet is in the form of a doublewall, the inner member of which is provided with openings.

In testimony whereof I have hereunto set my hand this th day ofDecember, A. D. r

EMIL FRIEDRICH RUSS.

